1. Field of the Invention
The present invention relates to the field of polymer compositions, and in particular to compositions comprising at least one thermoplastic elastomer. The polymer compositions of the invention are useful in articles of manufacture that require flexibility and are fabricated with adhesives, including sporting goods, and particularly athletic shoes.
2. Description of the Related Art
Several patents and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents and publications is incorporated by reference herein.
Thermoplastic elastomers are high value materials that offer desirable properties together with the convenience of melt processability and the environmental advantages of recycling. Several genera of thermoplastic elastomers are known. Two that have achieved commercial significance are the block copolymers of ethers and amides (copolyetheramides) and those of ethers and esters (copolyetheresters).
Copolyetheramides and copolyetheresters offer unique dynamic mechanical properties, such as maintaining constant flexibility over a wide temperature range, and maintaining toughness at very low temperatures. Thus, despite their high cost, these materials have found a particular utility in the sporting goods and athletic shoe industries. For example, copolyetheramides are widely used in shoe parts such as sole plates, shanks, and various other components in which low hysteresis and substantially ideal elastic recovery properties are required.
In compound structures that comprise parts made of thermoplastic elastomers, the thermoplastic elastomers are typically fastened to the other components of the structure with adhesives. In the fabrication of athletic shoes, for example, solvent-based adhesives are usually applied to the parts comprising copolyetheramides. The adhesion is generally adequate; however, adhesion failure is not uncommon, especially since constant bending and flexing is often required of the parts made from thermoplastic elastomers. Adhesion failure is a major product defect. Therefore, improving the adhesion of thermoplastic elastomeric parts is a significant goal.
More importantly, driven by environmental concerns, industry is gradually phasing out solvent-based adhesives and substituting water-based adhesives or hot-melt adhesives. In this regime, adhering copolyetheramides and copolyetheresters to other substrates becomes even more difficult. In fact, copolyetheramides simply fail to attain adequate adhesion with water-based adhesives.
In light of the foregoing, it will be appreciated that an ongoing need exists to maintain the desirable dynamic mechanical properties of thermoplastic elastomers while improving their economic efficiency and their adhesion, particularly with water based adhesives